The iPad and iPad Pro are great for many reasons, but I love them in part for helping me make paper documents and forms almost obsolete: I can't think of the last time I had to print a form and send it through the mail (or worse — fax it). Instead, I rely on iOS's built-in tools and great third-party apps to take care of all my form, document, and signature-related needs.
After testing a bunch of PDF markup apps — and asking for your favorites on Twitter, here are my top apps worth considering.
Preview may not exist on the iPad just yet, but its excellent markup and annotation tools are available systemwide in iOS as an extension since iOS 11. The Markup extension can be triggered by pressing either the Share button or new Markup button in certain apps — it looks like a pen tip with a circle around it. (You can also tap an email attachment in Mail, or take a screenshot to activate them.)
In the Markup interface, you can add pen, highlighter, or pencil notation; basic shapes like squares, circles, arrows, and quote bubbles; drop a magnifier on the image or document; and even add text or a signature.
It's basic, to be sure, but sometimes basic is all you need.
While putting together this roundup, I had a number of people point me in the direction of PDF Viewer, a newer annotation app released at the end of 2016. After a few minutes with the free app, it's clear why they did — between its clean, simplistic interface and powerful annotation tools, PDF Viewer is a perfect in-between for users who need a bit more than iOS's Markup tool provides, but don't need the power of apps like PDF Expert or LiquidText.
A PDF app's interface can frequently appear daunting to the average user, thanks in part to the sheer number of annotation options developers try to shove inside of them, but PDF Viewer smartly simplifies this process. Taking a page from Apple's own iWork suite, the app provides a series of nested views depending on which feature you're using. For instance, if you're looking at a document, you'll be shown the tools for sharing, zooming, and browsing through annotations; tap the annotation button, and the app brings you into Annotation mode, with its various tools — still simplified into easy-to-understand icons.
PDF Viewer can even rearrange, delete, or insert blank pages within a PDF, though it doesn't have some of the more advanced combination features (like merging multiple PDFs or adding existing PDF pages into a document).
Twitter, you did well to bring this app on my radar. It's an excellent one.
When people ask for an all-purpose PDF markup and annotation app, I tend to send them to Readdle and PDF Expert. The free download offers basic PDF reading, annotation, and digital signatures, but where it shines is in its advanced tools that you can get via in-app purchases.
You can create customizable "stamps" for oft-used annotations (a friend to copy editors everywhere), edit the structure of the PDF, zip multiple documents together, password-protect your files, and sync with iCloud. The Pro upgrade takes those tools one step further and allows you to physically crack open a PDF and edit it on the spot. Have a spelling error in your ready-to-print proof? Even if you can't jump back to InDesign on your iPad, you can fix it in the PDF.
You may never need the tools that PDF Expert provides, but I for one love that an app this complex and functional exists on iOS.
I've rewritten this intro to LiquidText about five times now, largely because the multitouch annotation app has this slippery way of defying description. A traditional sign-and-form-fill annotation app this is not: LiquidText is built for projects, novels, research papers, and dusty libraries. Lawyer and Mac enthusiast David Sparks describes it as being "engineered around the idea of reviewing long PDF documents better." It looks at books filled with post-it notes and string-covered bulletin boards and laughs. There's a better way to organize your research, and the app is it.
At its core, LiquidText focuses on the pain point of annotating lengthy documents, giving users a number of tools to do it in a way wholly unlike any other PDF app on the market. You can use multitouch gestures to pinch together large sections of a document; for instance, you could look an introductory thesis statement next to its midpoint argument to see if it properly connects the dots. You can pull annotations out from the document they belong to — like clippings or post-its — and organize them together or even link them along the right side of the screen. And all of this is lightning fast and wholly enjoyable, thanks to LiquidText's speedy and simple UI.
The Apple Pencil makes all of this even better, giving users specific gestures to highlight and pull out annotations as you review documents. For those who need this kind of workflow, there's no better app than LiquidText out there — and possibly no better workflow.
Smile Software brings us useful software like TextExpander and PDFPen. With PDFPen, you're able to instantly view, draw, highlight, add comments, fill, and sign pretty much any document you need, all while on-the-go with your iPad and Apple Pencil, and even your iPhone.
When adding highlights or freehand scribbles, the wrist/palm detection makes sure that you're only marking up the selected area that you want, and nothing else. It works great and you can insert notes and comments as needed throughout the document. Images can be resized, moved, copied, or deleted from documents, and you can import new ones from your Photo Library.
PDFPen is packed with a ton of useful features, including iCloud syncing, as well as third-party service support like Dropbox, Google Drive, Microsoft OneNote, and more. Documents can also be password protected and encrypted, and it also supports other styluses as well if you don't have an Apple Pencil.
Plus, PDFPen 5 is just a one-time fee, with no additional in-app purchases.
Want to maximize your productivity when it comes to PDFs and documents? Then iAnnotate is a great option to consider.
iAnnotate 4 does your basics, such as letting you open and view PDFs and documents, but you can do so much more with the app than what you may think. The biggest draw with iAnnotate is the iPad Pro multitasking support, allowing you to view two documents side-by-side. It will automatically annotate when you use an Apple Pencil, and you can pan, zoom, and scroll with your fingers at will, no tool switching needed, making it a streamlined experience. There are even keyboard shortcuts if you want to maximize efficiency.
All markups on your documents can be saved directly, letting you view markups in external PDF readers. The Flatten feature compresses annotations onto the document to prevent modifications from being made. A situation that this is great for is when there needs to be multiple signatures on a document, as the Flatten feature prevents others from making unauthorized modifications or changes.
Like PDFPen, iAnnotate 4 is a one-time purchase with no in-app purchases to worry about.
Other apps we tested
For this roundup, I narrowed down an incredibly large pool of PDF apps to highlight the best ones in their respective classes, which naturally meant excluding otherwise beloved apps. Here are some alternative PDF annotation apps that are great, but didn't quite make the cut.
- GoodReader ($6 with IAPs): GoodReader was my stalwart PDF manager and annotation editor for a long time, in large part because it supported uncompressing ZIP files, but I tend to look at it as more file management system than proper PDF annotation app.
- GoodNotes ($8) & Notability ($9 with IAPs): Both of these apps have PDF annotation features, but they're first and foremost note-taking apps.
- Pages (Free): Apple's own Pages has a Smart Annotation feature now, allowing you to markup documents as well.
Do you have a favorite PDF annotation app I missed? Let me know below so I can check it out for our next roundup!
November 2019: Added PDFPen 5 and iAnnotate 4 to the main list.
Serenity Caldwell contributed to an earlier version of this guide.
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